This invention relates to an improved electrical connector. More particularly, it relates to an improved interlock system for a plug and receptacle which houses an electrical switch.
For electrical connections in high current applications such as shipboard and/or dockside, it is quite often necessary to insure that one side of the line is deactivated while the contacts are exposed and during engagement and disengagement of the connector. This deactivation of power is to prevent arcing when the corresponding contacts of the plug and the receptacle of the connector are either engaged or disengaged with one another, and further, to provide a safety factor for personnel who may be in close proximity to the receptacle when the plug is removed, especially at wet locations. Arcing is bothersome because it causes corrosion of the contacts and, furthermore, in certain situations, such as certain gaseous environments, this arcing could cause an explosion.
Prior art attempts to overcome these problems include the use of a circuit breaker or electrical switch within the receptacle. A handle is placed on the outside of the receptacle, which must be turned to its off position prior to retraction or insertion of a corresponding plug. Thus, the switch opens the circuit between the receptacle contact and the high voltage conductor on the power source side of the switch. The main drawback of this device is that it is subject to human error, in that the person doing the connecting might forget to switch off the power prior to connecting/disconnecting the plug. Others have attempted to overcome this human error problem by the use of so called interlock systems.
One example of an interlock technique is shown in U.S. Pat. No. 1,934,024, issued to Anderson. The Anderson patent shows a junction box, which includes a receptacle and an electrical switch. A corresponding plug is adapted to be received in the receptacle. A rod is operably connected to the junction box switch, which is further connected to a latching device. The latching device latches to a boss on the outer periphery surface of the plug, which locks the plug into place when the power is turned on. By the use of this latch the power must be turned off in order for the plug to be removed. Thus, arcing is substantially eliminated upon withdrawal of the plug. However, one of the drawbacks of the Anderson patent is that the power may be turned on after the plug has been removed from the receptacle. Thus, the contacts of the receptacle may be tampered with the switch on, causing a safety hazard.
Another interlocked plug and receptacle is disclosed in U.S. Pat. No. 2,015,543, issued to Bissell. The Bissell patent shows a switch which is housed by the receptacle and operated by a handle on the receptacle. The handle is attached to a switching drive mechanism by a rod. When the plug is removed from the receptacle, a lock member maintains the rod in one position, i.e., the switch is kept off. However, once the plug has been inserted into the receptacle, the lock member rotates permitting the switch to be turned on. One of the drawbacks to the Bissell construction is that the lock member is internal to the receptacle and appears to be susceptible to jamming. Thus, it is impossible to see whether or not interlock mechanism is working to maintain the switch off when the plug is removed.